1. Field of the Invention
The invention relates to seals having removable sections to fit various size pipes, more specifically to a tear-start portion of a seal wall that has a weakened annular portion, for initiating and continuing the tear without damaging edges of the seal wall which are to seal about the pipe. The tear-start portion is in the plane of the seal wall and is engaged by puncturing the seal wall away from the weakened annular portion.
2. Description of the Prior Art
A septic tank or a septic system distribution box may have a plurality of seals with removable sections mounted in the walls of the tank or box. Sections of selected seals are removed to accommodate pipes through the seals, while the remaining seals must remain water tight.
In FIG. 1, Prior Art seal unit 20 is cast into opening 22 in concrete wall 24 of a septic tank. This is a frustoconical 26 seal unit with an adjustable annular seal wall 30. The wall is adjusted to fit pipes of different predetermined diameter by tearing out a portion of the wall that is slightly smaller than the outer diameter of the pipe. This provides a tight fit of the remaining part of the seal wall around the pipe.
Sections of wall 30 can be severed from the wall by inserting a screw driver 32 or similar pointed instrument through the wall at annular groove 34 or annular groove 36. If the wall is torn out at annular groove 34, section 38 is removed, shown as 38'. This leaves an opening of diameter 42 through seal wall 30.
If the screw driver is inserted through the wall at annular groove 36, an opening for larger pipe is made through seal wall 30.
Tools on a job site are often rusty, or roughened, a screw driver blade is not curved to fit the annular groove, and the blade and can be accidentally inserted crosswise to the groove. This results in damage of the edge of the groove. The damage of the edge of the groove causes a leak space between the edge of the seal wall opening and the pipe.
U.S. Pat. Nos. 4,805,920 and 5,286,040 patented Feb. 21, 1989 and Feb. 15, 1994 respectively by N. Gavin describe a septic tank seal comprising a wall having removable sections which are torn out along weakened narrow annular portions like grooves 34 and 36 by insertion of a tool through the wall at the groove as discussed above.
U.S. Pat. No. 5,036,636 patented Aug. 6, 1991 by W. Hasty describes a flashing collar adapted to seal against more than one size of a vent pipe passing through the collar by removal of sections of the collar wall along annular separation rings of reduced thickness compared to the collar wall. The ring from which the section is removed seals around the vent pipe. Each ring has a weakened portion of the collar wall against one side of the ring along a length of the ring, and a pull tab extends substantially vertically from the weakened portion at the side of the ring along a length of the ring for gripping by a pliers for tearing from the seal wall, the section of seal wall that is immediately surrounded by the ring from the seal wall.
Pulling the tab alongside the ring, up from the wall in order to initiate the tear at the weakened portion can distort the edge of the ring if the tab is pulled uniformly across its width.